A conventional torque absorbing device is disclosed in, for example, Japanese Patent Application Laid-Open Publication Nos. 58 (1983)-187623, and 59 (1984)-26625, and Japanese Utility-Model Application Laid-Open Publication No. 59 (1984)-166030. This torque absorbing device includes a hub member having a flange portion and plate members which are disposed around a hub portion of the hub member so as to be opposite to the flange portion. Each of the plate members and the flange portion of the hub member have a plurality of window portions each of which extends in the circumferential direction of the disc. The plate members are disposed so that their window portions overlap the window portions of the flange portion of the hub member. The hub member and the plate members are elastically connected to each other in the circumferential direction of the disc through a plurality of torsion members which are each disposed in the overlapped window portions so that an input torque is transmitted from the plate members to the hub member through the torsion members while being absorbed by a flexible contraction of each torsion member. In this conventional torque absorbing device, a seat member is disposed among an axial end surface of each of the torsion members, circumferential end surfaces of the window portions of the plate members, and the flange portion of the hub member. A supporting portion having a flange shape is formed on an edge portion of each window portion of the plate members and the seat members are prevented from relative movement with regard to the plate members by the supporting portions and the circumferential surfaces and the circumferential end surfaces of the window portions.
In the above known torque absorbing device, however, the seat members are not prevented from relative movement with respect to the hub member. Therefore, in the case where, for example, the torsion members are contracted by the torque through the plate members, the seat members located in the input side keep contacting the circumferential end surfaces of the window portions of the plate members in order to prevent movement. On the other hand, the seat members located in the output side are separated from the circumferential end surfaces of the window portions of the plate members. As a result, the seat members located in the output side can be moved with the torsion members in the diametrical and axial direction of the device by centrifugal force and the like. Accordingly, the seat members located in this movable side are pressed to the plate members and this movement of the seat members may cause wear.
A need exists, therefore, for a torque absorbing device which overcomes the above drawback.
It would be desirable to provide a torque absorbing device in which the wear of the seat member caused by the plate members is prevented.